DC-DC converter suitable for thermoelectric generator

Based on the magnetic coupling resonant wireless power transmission technology, how to improve the efficiency of the system under the condition of low voltage and high current input is studied. In this paper, a wireless power transfer system based on Z-source inverter is proposed. In the environment of low voltage and high current input, the input voltage is low, and the increase of DC-DC link will increase the loss of the system. Therefore, this paper analyzes the circuit of the magnetically coupled resonant wireless power transmission system in the low-voltage input and high-current output environment, and applies the Z-source inverter to the low-voltage and high-current input environment to improve the performance of the system.

In this paper a novel high output impedance, low input impedance, wide bandwidth, very simple mirror/source structure with input and output voltage requirements less than that of a simple current mirror is presented. It can be also used as variable negative impedance converter (variable-NIC) by modifying amplifier transistors' aspect ratios. The circuit's principle of operation is discussed and compared to simple and low voltage cascode (LVC) current mirrors. Working with power supplies less than 1volt, the proposed circuit provides output impedance greater than LVC current mirror. Such outstanding features of this current mirror as high output impedance~25.3M, low input impedance~44, wide bandwidth~498 MHz, low input voltage ~ 415 mV, low output voltage ~ 149 mV and low current transfer error ~1.3% (all at 10 ¿A) makes it an outstanding choice for high performance applications. Simulation results in BSIM 0.35 ¿m CMOS technology with Hspice are given in comparison with simple, and LVC current mirrors to verify and validate the performance of the proposed current mirror/NIC.

This paper presents the design of a digital controller for a 600 W Boundary-Conduction-Mode (BCM) interleaved boost converter used in an ac-dc Power-Factor-Correction (PFC) power supply. The output voltage of a typical boost PFC rectifier contains a 2nd harmonic ripple. Therefore to achieve good power factor, the output voltage compensator must have a low bandwidth, in order to sufficiently attenuate this 2nd harmonic component. As a result, the output voltage can suffer from poor transient response, especially at low input voltage. In this paper, a small-signal model of the output voltage dynamics is derived, where it is shown the open-loop gain of the system decreases with low input voltage. As a result, the output voltage transient response also deteriorates at low levels of input voltage. This can lead to poor voltage transient response for boost PFC converters that are designed to have an operating input line voltage range from 85 to 265 V. Having poor output voltage transient response is undesirable as it can lead to high peak over shoot on the output capacitors, or even worse, lead to an output voltage tracking failure. To correct this behaviour, an adaptive digital voltage compensator is designed to change gain at low input voltage, to ensure the output voltage maintains good transient response. Finally, the derived small-signal analysis, and output voltage compensator performance are experimentally verified on a 600 W interleaved BCM converter.

A New CMOS resistor based current mirror with extremely low voltage requirement at input (in the range of a few mV) and output voltage requirement of about one V ds is presented. The proposed structure combines the advantages of wide input swing, wide output swing, large output impedance, low input impedance and high linearity altogether, which make it attractive for high performance low-voltage and low power applications. Pspice simulations show a very low THD of −42.2dB from a single 0.9V supply in 0.18µm, input impedance of 239Ω, output impedance of 1.2MΩ and power dissipation of only 180µW. Interestingly, the input and output voltage requirements are only 10mV and 0.1V respectively.

This paper proposes a low input voltage charge pump using 0.18um CMOS process for energy harvesting. There are two main sections in the charge pump system: Low Voltage Charge Pump (LVCP) and High Voltage Charge Pump (HVCP). In the LVCP, a negative charge pump is utilized to improve the efficiency at low input voltage, Dynamic Body Bias (DBB) and switch-conductance enhancement techniques are applied to a unit stage of the two-stage charge pump. In the HVCP, the charge pump circuit utilizes charger transfer switches (CTS) with a complementary banch scheme to significantly reduce undesired charge transfer, and an optimized gate control strategy is applied to further decrease the power loss caused by undesired charge transfer. The simulation result demonstrates that the proposed circuit can achieve 97% voltage conversion and drive 800uA load current at 0.6V input voltage. In the region of 0.4V to 0.6V input voltage, the circuit performs well with the load resistance of 10K ohms.

This paper presents a novel control method to improve the efficiency of low-voltage DC-DC converters at light loads. Pulse Width Modulation (PWM) converters have poor efficiencies at light loads, while pulse frequency modulation (PFM) control is more efficient for the same cases. Switching losses constitute a major portion of the total power loss at light loads. To decrease the switching losses and to increase efficiency, converters based on soft-switching are utilized. This paper presents the design of a soft-switching DC-DC buck converter in a 90-nm CMOS technology. Simulation results by HSPICE shows a 21 mV output ripple on a 0.5 V output voltage for an input voltage of 1.4 V. Finally, the efficiency of 95% at a load current of 50 mA having 74 mA of current ripple is achievable.

Thermoelectric generators: Linking material properties and systems engineering for waste heat recovery applications

The comparative performance of phase-shift modulated parallel tuned resonant DC/DC converter topologies is described. Three converter topologies (Type-A, Type-B and Type-C) are presented. The Type-A converter uses a series-tuned and parallel off-tuned resonant circuit. This converter topology exhibits near zero switching losses, at the expense of increased conduction losses. The Type-A converter is better suited for very high operating frequency and low input voltage with narrow range of variation. In the Type-B converter, both the series and parallel branches of the resonant circuit are tuned at the operating frequency. In this topology, 6 out of 8 switching losses are eliminated without additional penalty on the conduction losses. The Type-B converter is better suited for medium operating frequency and low input voltage with wide variation. The resonant circuit employed in the Type-C converter consists of a series inductor and a tuned parallel branch. In this topology, near zero switching losses are achieved without causing increased conduction losses. The Type-C converter topology is better suited for a very high operating frequency and high input voltage with wide variation. >

The smooth impact drive mechanism (SIDM) actuator is traditionally excited by a saw-tooth wave, but it requires large input voltages for high-speed operation and load capacity. To improve the output characteristic of the SIDM operating at low input voltage, a novel driving method based on ultrasonic friction reduction technology is proposed in this paper. A micro-amplitude sinusoidal signal with high frequency is applied to the rapid deformation stage of the traditional saw-tooth wave. The proposed driving method can be realized by a composite waveform that includes a driving wave (D-wave) and a friction regulation wave (FR-wave). The driving principle enables lower input voltage to be used in normal operation, and the principle of the proposed driving method is analyzed. A prototype of the SIDM is fabricated, and its experimental system is established. The tested results indicate that the actuator has suitable velocity and load characteristics while operating at lower input voltage, and the load capacity of the actuator is 2.4 times that of an actuator excited by a traditional saw-tooth driving wave.

Power factor correction (PFC) is widely used in ac–dc converters to improve power quality. The current-source charge pump (CS-CP) PFC converter has the advantages of simple structure, easy control, and low cost, but it can only obtain a high power factor (PF) over a narrow input range. The operation principle of the CS-CP PFC converter and the input voltage range are analyzed in this article. In order to obtain a high PF over a wide input voltage range, in this article, a variable turn ratio CS-CP PFC converter is proposed. By adjusting the turn ratio according to the variation of the input voltage, the proposed converter can obtain a high PF over a wide input voltage range, reduce the voltage stress of the bus capacitor, and solve the problem of insufficient voltage gain at low input voltage. The operating modes and the wide input voltage range of the proposed converter are analyzed, and the relevant parameters are given. A 40-W experimental prototype operating with the input voltage range of 100–242 Vac is built to verify the theoretical analysis. The proposed converter obtains the PF of 0.946–0.991 and its total harmonic distortion of current can satisfy the IEC 61000-3-2-2020 Class-C Standard in the whole input voltage.

The two-switch buck-boost (TSBB) converter is suitable for wide input voltage applications. In order to achieve high efficiency over the entire input voltage range, the TSBB converter is operated in buck mode at high input voltage and boost mode at low input voltage. Such operation is called the two-mode control scheme. The objective of this paper is to propose an input voltage feed-forward (IVFF) method to reduce the influence of the input voltage disturbance on the output voltage. The small-signal models of the TSBB converter are built, and based on which, the IVFF functions under different operating modes of the TSBB converter are derived. The IVFF function in boost mode is simplified for easy implementation. The two-mode control scheme with IVFF compensation is then proposed for the TSBB converter, which realizes automatic selections of operating modes and the corresponding IVFF functions. Besides, nearly smooth switching between buck and boost modes is also guaranteed. For exhibiting the advantages of the proposed control scheme clearly, comparisons between the two-mode control with and without IVFF compensation have been presented in this paper, including the output signal of the voltage regulator and input-to-output voltage transfer function. Finally, a 250−500-V input, 360-V output, and 6-kW-rated power prototype is fabricated to validate the effectiveness of the proposed control scheme in the laboratory, and the experimental results show that the TSBB converter has an improved input transient response and high efficiency over the entire input voltage range with this proposed control scheme.

Thermoelectric generators (TEGs) are now capable of powering the abundant low power electronics from very small (just a few degrees Celsius) temperature gradients. This factor along with the continuously lowering cost and size of TEGs, has contributed to the growing number of miniaturized battery-free sensor modules powered by TEGs. In this article, we present the design of an ambient-powered wireless bolt for high-end electro-mechanical systems. The bolt is equipped with a temperature sensor and a low power RF chip powered from a TEG. A DC-DC converter interfacing the TEG with the RF chip is used to step-up the low TEG voltage. The work includes the characterizations of different TEGs and DC-DC converters to determine the optimal design based on the amount of power that can be generated from a TEG under different loads and at temperature gradients typical of industrial environments. A prototype system was implemented and the power consumption of this system under different conditions was also measured. Results demonstrate that the power generated by the TEG at very low temperature gradients is sufficient to guarantee continuous wireless monitoring of the critical fasteners in critical systems such as avionics, motorsport and aerospace.

In this review work, energy harvesting methods for waste heat with small temperature differences between heat source and sink are discussed. At present, many methods are tried and employed to utilize this type of waste heat. A typical example is found in a conventional power generation system. By utilizing this type of waste heat, additional energy can be produced in regular power generation systems. Up to this point, two energy harvesting methods have been introduced and applied for the use with this type of waste heat. One is a method using an organic Rankine cycle (ORC) while the other is a method using a thermoelectric generation (TEG). An ORC is a Rankine cycle that can be applied to this type of waste heat using organic fluids such as refrigerants as working fluids instead of water used in a typical Ranking cycle. On the other hand, a TEG utilizes Peltier, Seebeck, and Thomson effects caused by the temperature difference between the heat source and sink for energy harvesting. In this work, various aspects associated with the use ORC and TEG for waste heat harvesting with small temperature differences between the heat source and sink.

Thermoelectric power generation has emerged as a promising alternative green technology for the power generation from waste-heat. Thermoelectric devices generate voltage and output electrical power from waste heat to electronic load by meansof the temperature difference across the devices serving as anenergy source. This paper presents the high gain DC-DC boost converter, that has the coupled inductor with voltage multiplier produces a high voltage gain from very low input voltages of Thermo Electric Generator (TEG) for a moderate duty cycle to reduce voltage and current stresses within the converter. In this investigation, 16W TEG module (TEP1-12656-0.6) is used as a DC source to analyze the proposed converter for various temperature differences (ΔT = 270°C, 245°C, 195°C, 145°C, 95°C, 45°C). A MPPT method of tracking the maximum power point and forcing the system to operate close to this point is used at ΔT=270°C using a Perturb and Observe (P&O) and Incremental Conductance (INC) algorithm. The proposed high gain DC-DC converter is simulated using PSIM 9.0 software package. Analysis and simulation are carried out, and the measured results are presented here for validity of the proposed technique.

A ring oscillator (ROSC) for extremely low-voltage thermoelectric energy generators is presented. The ROSC is composed of dedicated low-voltage stacked body bias inverters (SBBIs) that are based on the conventional self-bias inverter (SBI) and stacked inverter (SI). The proposed SBBI employs the advantages of both SBI and SI to oscillate at extremely low supply voltage $(V_{\mathrm{D}\mathrm{D}})$ . The voltage gain $\vert A_{\mathrm{I}\mathrm{N}\mathrm{V}}\vert$ of our proposed SBBI is improved and enhanced by controlling main inverter's supply $(V_{\mathrm{D}\mathrm{D}}$ and Gnd) and body-bias voltages, by using stacked and feedback inverters. Simulated results using a standard 0.18 $\mu \mathrm{m}$ CMOS process with deep N-well option showed that our proposed ROSC could oscillate at extremely low $V_{\mathrm{D}\mathrm{D}}$ of 34 mV and generate a clock pulse with a 88% voltage swing from an input $V_{\mathrm{D}\mathrm{D}}$ of 50 mV.